Described are alkyl-substituted spiroundecenone derivatives defined according to the structure: ##STR1## wherein R.sub.1 represents isopropyl or hydrogen; R.sub.2, R.sub.3 and R.sub.4 are the same and each represents methyl or hydrogen; with the provisos that:(i) when R.sub.1 is isopropyl, R.sub.2, R.sub.3 and R.sub.4 are hydrogen; and(ii) when R.sub.2, R.sub.3 and R.sub.4 are each methyl, R.sub.1 is hydrogen,and uses thereof in augmenting or enhancing the aroma of perfume compositions, colognes and perfumed articles including but not limited to solid or liquid anionic, cationic, nonionic or zwitterionic detergents, fabric softener compositions, fabric softener articles and hair preparations; as well as processes for preparing said alkyl-substituted spiroundecenone derivatives.